xbmc/xbmc — comment on commit d1c5773a2736849616adda4013d1a8c5a56a84e6
File: xbmc/music/karaoke/karaokevideobackground.h line 77
By davilla:

class m_dllAvFormat;
class m_dllAvCodec;
class m_dllAvUtil;
class m_dllSwScale;
struct AVFormatContext;
struct AVCodecContext;
struct AVCodec;
struct AVFrame;

Hardly ambiguous and is the standard way to do forward declares :)